The ability to measure signals from a living subject (e.g., relating to the living subject's bodily functions) is beneficial for medical and diagnostic applications as well as for scientific research. For example, from a diagnostic point of view, measuring brain signals helps to ascertain brain activity related to abnormal brain function, to monitor spatial and/or temporal progression of brain disease, to aid surgical or nonsurgical intervention by localizing disease-sites in the brain, and to monitor brain activity of a healthy subject or a subject of unknown health status when the subject experiences a variety of stimuli and lack of stimuli. Likewise, measuring heart signals helps to diagnose both chronic and acute cardiac arrhythmias, other deficits in cardiac function, and potentially to monitor heart activity of a healthy subject or a subject of unknown health status when the subject experiences a variety of stimuli and lack of stimuli. From a scientific perspective, the ability to measure and study signals from a living subject (e.g., a human subject) facilitates scientific research aimed at understanding the structure and function of the human body.